As far I understood lib folder could used to place inside it some external libraries that can references through LIBRARIES variable.
In my case I would to create a project that contains 1 executable and 1 library where the executable in fact is a demo and test of that library, so that I can use the makefile either to run the app or simply to build the library for other usages.
I changed my Makefile follow way but I would to know if I miss something because its sound to me like an hack respect what this extension would provide, I'm wrong ?

As far I understood lib folder could used to place inside it some external libraries that can references through LIBRARIES variable.
In my case I would to create a project that contains 1 executable and 1 library where the executable in fact is a demo and test of that library, so that I can use the makefile either to run the app or simply to build the library for other usages.
I changed my Makefile follow way but I would to know if I miss something because its sound to me like an hack respect what this extension would provide, I'm wrong ?